System and method for constructing heat exchanger

ABSTRACT

The present invention generally relates to various types and/or structures of heat exchangers and to methods of making and/or using such heat exchangers. In one embodiment, the present invention relates to a system and method for constructing a microchannel gas-to-working fluid heat exchanger. In another embodiment, there is disclosed a power generation cycle that employs a heat exchanger that serves as a regenerative heat exchanger.

RELATED APPLICATION DATA

This application is related to, and claims priority from, previously filed U.S. Provisional Patent Application No. 61/209,055 entitled “System and Method for Constructing Heat Exchanger,” filed Mar. 2, 2009, the entirety of which is hereby incorporated by reference herein.

FIELD OF THE INVENTION

The present invention generally relates to various types and/or structures of heat exchangers and to methods of making and/or using such heat exchangers. In one embodiment, the present invention relates to a system and method for constructing a microchannel gas-to-working fluid heat exchanger. In another embodiment, there is disclosed a power generation cycle that employs a heat exchanger as disclosed and claimed herein as a regenerative heat exchanger, a waste heat exchanger and/or a condenser.

BACKGROUND OF THE INVENTION

Current gas/working fluid heat exchangers are similar to automobile radiators and are based on finned tubes. The tubes may be circular or elongated. Heat transfer between the gas and fluid (air, combustion gas, waste heat, etc) is by conduction through metal fins attached to the tubes. Although the current state of the art yields a fairly effective heat transfer circuit, recent advances in microchannel technology offer potential significant improvement in heat exchanger size and effectiveness through virtually eliminating the fin conduction path by flowing the working fluid through the fins themselves.

Given the above, there is a need in the art for an improved thermal management system, such as an improved heat exchanger as disclosed and claimed herein, to address various thermal management issues present in various applications in which heat exchangers are used, including but not limited to, energy recapture systems.

SUMMARY OF THE INVENTION

The present invention generally relates to various types and/or structures of heat exchangers and to methods of making and/or using such heat exchangers. In one embodiment, the present invention relates to a system and method for constructing a microchannel gas-to-working fluid heat exchanger. In another embodiment, there is disclosed a power generation cycle that employs a heat exchanger as disclosed and claimed herein as a regenerative heat exchanger, a waste heat exchanger and/or a condenser.

In one embodiment, the present invention relates to a thermal management system as shown and described herein, wherein the thermal management system is based on, includes, or is a heat exchanger.

In another embodiment, the present invention relates to a method for constructing and/or producing a thermal management system as shown and described herein, wherein the thermal management system is based on, includes, or is a heat exchanger.

In still yet another embodiment, the present invention relates to a heat recovery system that utilizes at least one regenerator based on microchannels, mesochannels, and/or minichannels.

In still yet another embodiment, the present invention relates to a heat recovery system that utilizes at least one regenerator, wherein the at least one regenerator is based on one or more printed circuit heat exchange (PCHE) panels.

In still yet another embodiment, the present invention relates to a gas-to-working fluid heat exchanger comprising: (a) a plurality of fins designed to contain at least one working fluid, wherein each of the plurality of fins contain therein one or more microchannels, mesochannels, or minichannels designed to permit the movement of the at least one working fluid through the one or more microchannels, mesochannels, or minichannels; (b) the plurality of fins being arranged in a horizontally and vertically spaced array or stages with an “offset strip” geometry so that heat transfer on the gas side of the heat exchanger is enhanced by frequent break-up of the fluid boundary layer, creating a turbulent boundary layer at the upper and lower heat transfer surfaces downstream of and/or adjacent to the microchannel fins; and (c) a plurality of cross-flow and/or counter-flow working fluid paths designed to permit the progression of working fluid flow through adjacent sets and/or stages of fins in the heater core in order to create a counter-flow to the flow of the gas through the heat exchanger thereby resulting in a heat exchanger having a core effectiveness that is more effective than either a conventional counter-flow or cross-flow heat exchanger geometry.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a microchannel gas/working fluid heat exchanger in accordance with one embodiment of the present invention;

FIG. 2 is an illustration of one production method for a microchannel gas/working fluid heat exchanger in accordance with one embodiment of the present invention; and,

FIG. 3 is an illustration of one use for a heat exchanger formed in accordance with any one of the embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally relates to various types and/or structures of heat exchangers and to methods of making and/or using such heat exchangers. In one embodiment, the present invention relates to a system and method for constructing a microchannel gas-to-working fluid heat exchanger. In another embodiment, there is disclosed a power generation cycle that employs a heat exchanger that serves as a regenerative heat exchanger.

As used herein, the terms “microchannels,” “mesochannels,” and/or “minichannels,” although not identical in meaning and scope, are utilized interchangeably. Additionally, the microchannels, mesochannels, and/or minichannels of the present invention are not limited to any one particular size, width and/or length. Any suitable size, width or length can be utilized depending upon a variety of factors including, but not limited to, microchannels, mesochannels, and/or minichannels having variable sizes and/or lengths. Furthermore, any orientation of the microchannels, mesochannels, and/or minichannels can be utilized in conjunction with the various embodiments of the present invention.

As is discussed above, current gas/working fluid heat exchangers are similar to automobile radiators and are based on finned tubes. The tubes may be circular or elongated. Heat transfer from the gas (air, combustion gas, waste heat, etc) is by conduction through metal fins attached to the tubes. Although the current state of the art yields a fairly effective heat transfer circuit, recent advances in microchannel technology offer potential significant improvement in heat exchanger size and effectiveness through virtually eliminating the fin conduction path by flowing the working fluid through the fins themselves.

Thus, in one embodiment, the present invention relates to an improved heat exchanger that utilizes microchannel technology. In this embodiment, an improved heat exchanger is disclosed for transferring heat from an environment to a working fluid, or from the working fluid to the environment (see, e.g., FIG. 1). In one instance, the working fluid of this embodiment includes, but is not limited to, a gas and/or supercritical gas or fluid. In one instance, the gas of the present invention includes, but is not limited to, ambient air, hot air, cold air, carbon dioxide, nitrogen, helium, combustion gases or waste heat exhaust. In another instance, the supercritical gas or fluid is formed from, or is, carbon dioxide, helium, nitrogen, air, etc. Although the current state of the art yields a fairly effective heat transfer circuit, recent advances in microchannel technology offer potential significant improvements in heat exchanger size and weight reduction and increased effectiveness through virtually eliminating the fin conduction path by flowing the working fluid through the fins themselves.

Thus, in this embodiment, the present invention relates to a gas-to-working fluid heat exchanger featuring: (a) direct flow of the working fluid through strip fins containing a plurality of microchannels, mesochannels, minichannels or similar means; (b) a plurality of strip fins arranged in a horizontally and vertically spaced array or stages with an “offset strip” geometry so that heat transfer on the gas side of the heat exchanger is enhanced by frequent break-up of the fluid boundary layer, creating a turbulent boundary layer at the upper and lower heat transfer surfaces downstream of and/or adjacent to the microchannel fins; and/or (c) a serial cross-flow and/or counter-flow geometry for the working fluid so that, although the gas flows over each fin in cross-flow to optimize gas side heat transfer, the progression of working fluid flow through adjacent stages of strip fins in the heater core simultaneously creates a counter-flow to the flow of the gas through the heat exchanger resulting in an overall heat exchanger core effectiveness that is more effective than either a conventional counter flow or cross-flow heat exchanger geometry.

In one instance, the disclosed invention can be utilized to heat or cool a working fluid flowing through the strip fins of the heat exchanger, depending upon the temperature of the gas flowing over the strip fins. In one embodiment, the heat exchanger of the present invention can be used to remove waste heat from a hot gas stream and transfer the heat into a working fluid. In still another embodiment, the heat exchanger of the present invention can be used to remove heat from a working fluid by passing a colder gas over the strip fins. An additional embodiment of the present invention is designed to remove heat from a working fluid and may incorporate a motor-driven fan local to the heat exchanger to create a standalone fan-cooled condenser with optimized heat exchanger effectiveness and pressure drop of the gas and/or working fluids as it flows through the heat exchanger.

Given the above, the present invention is a heat exchanger that comprises a plurality of microchannel fins and header blocks so that the fins interlock with the header blocks and the blocks can be stacked to build a heat exchanger core of any number of fins. One embodiment of the present invention utilizes microchannel fins of varying widths, varying lengths, varying horizontal spacing, varying vertical spacing, varying fins per stage, or varying number of fin stages to optimize heat exchanger effectiveness for a given set of gas and working fluid combinations.

In another embodiment, the present invention relates to a heat exchanger that comprises multiple heater cores that utilizes multiple heat exchanger cores, as described above, that utilize microchannels of varying widths, varying lengths, varying horizontal spacing, varying vertical spacing, varying channels per stage and/or unit of area, varying channel orientation, or varying number of channel stages to optimize heat exchanger effectiveness for a given set of gas and working fluid combinations. In this manner, the present invention yields a multiple core heat exchanger that possesses improved heat exchanger effectiveness compared to conventional heat exchangers. In still another embodiment, heater core number and sizing may be varied to scale up or scale down the overall heat exchanger size and heat transfer capacity.

It should be noted that with regard to each individual core, the geometry and/or shape thereof is not limited to any one particular orientation. Rather, any suitable geometry or shape can be utilized in conjunction with the present invention.

It should be noted that the geometric shape of the fins in the present invention is not limited to any one specific geometrical shape. Instead, any suitable geometric fin shape can be utilized in conjunction with the present invention. Such shapes include, but are not limited to, circular, rectangular, square, polygonal, or elongated in external cross-section shape. In another embodiment, the plurality of microchannels, mesochannels, and/or minichannels within the strip fins can have a cross-sectional shape that is circular, rectangular, square, polygonal, or elongated in shape.

In still another embodiment, the present invention relates to a system that utilizes a combination of the above disclosed features to accomplish the goal of creating an improved heat exchanger. For example, additional embodiments can include the specific selection and combination of the above mentioned embodiments to optimize heat exchanger effectiveness and pressure drop of the gas and/or working fluids as it flows through the heat exchanger.

In one such embodiment, the present invention is comprised of header blocks so that the fins interlock with the header blocks and the blocks can be stacked to build a heat exchanger core of any number of fins. The header blocks contain a plurality of openings that act as inlet and outlet manifolds for transferring the working fluid to the flow passages inside the strip fins. The header blocks route the working fluid through the strip fins in a serial and parallel fashion to enable the working fluid to counter flow and cross flow to the gas flowing over the strip fins to optimize heat exchanger effectiveness and pressure drop. Each strip fin includes a plurality of openings at either end of the strip fin that connect the microchannels to the header blocks.

In keeping with the embodiments of this invention, an exemplary process for manufacturing a heat exchanger in accordance with the present invention comprises assembling the fins strips and header blocks together using diffusion bonding, brazing, welding, structural adhesive bonding, or similar joining methods.

In another embodiment, another manufacturing method comprises the fabrication of strip fins from a sheet material stock that can have the microchannels formed into one or both faces of the sheet via chemical etching, laser machining, roll-forming, stamping or similar forming methods. The formed sheet can be joined to a simple flat cover sheet or another formed sheet to enclose the microchannels using diffusion bonding, brazing, welding, structural adhesive bonding, or similar joining methods.

In another embodiment, a manufacturing method in accordance with the present invention comprises strip fins fabricated from extruded material with an appropriate microchannel geometry formed directly and enclosed into the fin during extrusion.

As an example for another manufacturing method, such a method comprises header blocks that are fabricated from sheet material stock with manifold features formed into the sheet using chemical etching, laser machining, roll-forming, stamping or similar forming methods.

Turning to the Figures, FIG. 1 is an illustration of a heat exchange formed in accordance with one embodiment of the present invention, while FIG. 2 is an illustration of one method of forming a heat exchange of FIG. 1.

It should be noted that the heat exchangers of the present invention can be used for various applications including, but not limited to, a regenerator in a system where waste heat is recaptured and “reused.” One example of such an embodiment is disclosed in FIG. 1.

In FIG. 3, another type of heat exchanger is disclosed where this heat exchanger is suitable, for use, among other applications, as a regenerative heat exchanger. By “regenerative heat exchanger” it is meant that heat, including even what would normally be waste heat, is recaptured and reutilized within a closed system using a working fluid. In one embodiment, the working fluid of this embodiment includes, but is not limited to, an inert gas such as carbon dioxide, nitrogen, helium, air, etc. that is in either gas form, or in a supercritical fluid form. In one specific embodiment, a supercritical fluid, or supercritical gas, formed from carbon dioxide is utilized as the working fluid.

In one embodiment, a heat exchanger in accordance with the present invention can be formed with one or more cores having one or more printed circuit heat exchange (PCHE) panels. Such panels are known in the art, and are described in U.S. Pat. Nos. 6,921,518; 7,022,294; and 7,033,553, all of which are incorporated herein by reference, in their entireties, for their teachings related to printed circuit heat exchange (PCHE) panels. Other suitable heat exchangers for use as a regenerator in the system of FIG. 3 are disclosed in United States Published Patent Application No. 2006/0254759, the disclosure of which is incorporated herein in its entirety.

The orientation and/or geometry of the cores is, in one instance, selected to maximize the thermal transfer between the working fluid (such fluids being those detailed above) at temperature 1 and the same, or a different, working at temperature 2. Depending upon the orientation of the system of FIG. 3, either temperature 1 or temperature 2 could be greater than the other remaining temperature. In one instance, the difference between two temperatures of the present invention is at least one degree Celsius. In this embodiment, the pressure used in the regenerators of this embodiment is in the range of about 500 to 7500 psi, inclusive.

In FIG. 3, a power generation system 100 is illustrated. In system 100 of FIG. 3 comprises a pump 102, a regenerator 104, a generator 106, an expander 108, and a condenser 110. All of the elements in system 100 are connected via a suitable transfer means that carries a working fluid. The nature of the working fluid is as described above. Regarding the transfer means, such means include, but are not limited to, piping, conduit, tubes, etc. In FIG. 3, the transfer means is a piping 112 that is capable of carrying a pressurized working fluid. In one instance, the pressure in piping 112 falls within the range of about 400 to about 3,500 psi, inclusive. In one embodiment, the pressure at P1 is in the range of about 400 to about 1,300 psi and the pressure at P2 is in the range of about 1,700 to about 3,500 psi. It would be apparent to those of skill in the art, that a pressure differential must exist through piping 112 in order to drive system 100.

In another embodiment, the present invention relates to a gas-to-working fluid heat exchanger comprising: (a) a plurality of fins designed to contain at least one working fluid, wherein each of the plurality of fins contain therein one or more microchannels, mesochannels, or minichannels designed to permit the movement of the at least one working fluid through the one or more microchannels, mesochannels, or minichannels; (b) the plurality of fins being arranged in a horizontally and vertically spaced array or stages with an “offset strip” geometry so that heat transfer on the gas side of the heat exchanger is enhanced by frequent break-up of the fluid boundary layer, creating a turbulent boundary layer at the upper and lower heat transfer surfaces downstream of and/or adjacent to the microchannel fins; and (c) a plurality of cross-flow and/or counter-flow working fluid paths designed to permit the progression of working fluid flow through adjacent sets and/or stages of fins in the heater core in order to create a counter-flow to the flow of the gas through the heat exchanger thereby resulting in a heat exchanger having a core effectiveness that is more effective than either a conventional counter-flow or cross-flow heat exchanger geometry.

In still another embodiment, the heat exchanger of the present invention can be utilized in one or more locations in the waste heat engine embodiments disclosed in U.S. patent application Ser. No. 12/631,379, filed Dec. 4, 2009, the entirety of which is hereby incorporated by reference herein.

Although the invention has been described in detail with particular reference to certain aspects detailed herein, other aspects can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art, and the present invention is intended to cover in the appended claims all such modifications and equivalents. 

1. A gas-to-working fluid heat exchanger comprising: (a) a plurality of fins designed to contain at least one working fluid, wherein each of the plurality of fins contain therein one or more microchannels, mesochannels, or minichannels designed to permit the movement of the at least one working fluid through the one or more microchannels, mesochannels, or minichannels; (b) the plurality of fins being arranged in a horizontally and vertically spaced array or stages with an “offset strip” geometry so that heat transfer on the gas side of the heat exchanger is enhanced by frequent break-up of the fluid boundary layer, creating a turbulent boundary layer at the upper and lower heat transfer surfaces downstream of and/or adjacent to the microchannel fins; and (c) a plurality of cross-flow and/or counter-flow working fluid paths designed to permit the progression of working fluid flow through adjacent sets and/or stages of fins in the heater core in order to create a counter-flow to the flow of the gas through the heat exchanger thereby resulting in a heat exchanger having a core effectiveness that is more effective than either a conventional counter-flow or cross-flow heat exchanger geometry.
 2. The heat exchanger of claim 1, wherein the working fluid is at least one gas and/or supercritical gas or fluid.
 3. The heat exchanger of claim 1, wherein the working fluid is selected from ambient air, hot air, cold air, carbon dioxide, nitrogen, helium, combustion gases or waste heat exhaust.
 4. The heat exchanger of claim 1, wherein the working fluid is selected from carbon dioxide, helium, nitrogen, air, ammonia, or combinations of two or more thereof.
 5. A thermal management system as shown and described herein, wherein the thermal management system is based on, includes, or is a heat exchanger.
 6. A method for constructing and/or producing a thermal management system as shown and described herein, wherein the thermal management system is based on, includes, or is a heat exchanger. 